Dredge trommel



Oct. 6, 1953 QLSON 2,654,481

DREDGE TROMMEL Zmnentor flaw/m2 045m (Ittorneg Patented Oct. 6, 1953 UNITED STATES PATENT OFFICE 2,654,481 DREDGE TKGMMEL Edward Ols eattle, ash Application January 15, 1951, Serial No. 206,069 (o1. ans-.291)

i i s- 1 My invention relates to devices primarily useful in separating fine material from coarser particles, such as the valuable fines from alluvial gravel and the like and is particularly concerned with a perforate, rotary trommel as adapted for utilization on a dredge, such as a gold or platinum dredge.

A dredge trommel usually comprises a rotating, circular-cylindrical shell having apertures of different size throughout its length except for certain areas or zones in which the shell wall is solid or imperforate, these zones usually being located in the vicinity of supporting rings encompassing the revolving shell. The capacity of a trommel of a given length is limited by the amount of perforate area that it is possible to include. Partic ularly aboard a dredge where room is quite limited, it is a difficult matter to provide a trommel having suflicient screen capacity.

It is therefore an object of my invention to provide a trommel having a capacity increased ove the normal or usual amount.

Another object of my invention is to provide a trommel in general similar to those normally provided but in which substantially all of the area of the rotating member is effective in the screening operation.

Another object of my invention is to provide a trommel in which various parts travel at various peripheral speeds to assist in the separating operation.

A still further object of my invention is to provide a trommel in which the interior construction assists in turning and working the material travelling lengthwise within the trommel.

A further object of the invention is in general to improve trommel mechanisms.

Other objects, together with the foregoing, are attained in the embodiment of the invention described in the accompanying description and illustrated in the accompanying drawings, in which Figure 1 is a side elevation of the exterior of a trommel constructed in accordance with my invention, the two end portions of the device being broken off to reduce the size of the figure.

Figure 2 is a cross section, the plane of which is indicated by the line 2'--2 of Figure 1.

Figure 3 is a cross section of a detail, the plane of cross section being indicated by the line 3-3 of Figure 2.

While the trommel of my invention can be embodied in a number of different ways and is susceptible to numerous variations, particularly dependent upon the type of material being handled and the particular style of dredge on which it is employed, 1 have;- used it successfully in the form illustrated, particularly on an alluvial dredge operating in materialcarrying platinum as a-value.

The trommel 6 is a generally circular-cylindrical, elongated shell arranged to revolve about a central axis '1' which, when installed on a dredge, is tilted downwardly toward the right in Figure 1. Material to be screened is introduced into the interior of the circular shell. at the lefthand end. as seen in Figure 1, and travels throughout the length of the shell, at least in part, for ultimate discharge over or out of the righthand end. Particles which are small enough to pass through openings in the shell are discharged radially or laterally.

At a convenient point on the dredge hull, there is provided a framework 8 on which supporting rollers 9 and ID are disposed. A number of such rollers are afforded, the ones illustrated being typical. Resting on and adapted to revolve with respect to the rollers 9 and ID is a support ring l2 of relatively heavy material. The ring l2. encompasses and is fastened to the outer shell is of the-trommelv 6. A number of such rings l2 are provided at appropriate-intervals along the length of the device. For much of its length, the shell is comprised of perforated screen plate It. These are preferably metal members drilled with appropriate sized apertures I! and then curved to the proper curvature and secured in place by fastenors l8. The size of the apertures I! is relatively small toward the leithand, upper end of the rotating trommel 6 and may be maintained or increased in size as the lower, righthand en is approached. I

Included in the shell adjacent the supporting ring [2 and in the vicinity of the other rings like it, is an imperiorate section 2i comprised of plates that are curved like the plates 16 and are similarly fastened in- Place but that are provided with no apertures. The prime reason for this is that apertures adjacent the ring I 2 permit fine material to pass through and to interpose themselves between the ring and the rollers 9 and N). This interferes with the appropriate rotation and operation of the trommel. Normally, the imperforate section 2| extends for a considerably distance on opposite sides of the ring [2 and being ineffective as a screening mechanism, substantially curtails the screening capacity.

In accordance with my invention, I preferably provide adjacent the opposite ends of the imperforate section 2| a pair of internal supporting members 22 and 23. These are either complete annuli or segments included in or secured to the outer shell 6. Disposed on the inner margins of the supporting rings 22 and 23 is a series of internal screen plates 24 fabricated of members appropriately drilled to provide apertures 26 and then bent to an appropriate curvature less than that of the shell 6. The plates are fastened by bolts 2'! and fasteners 28 and appropriate spacing tubes 29 are inserted at intervals so that an annular space 3| is left between the interior tube 24 and the outside shell of the trommel.

Material passing lengthwise down the interior of the revolving shell travels over the slight barrier imposed by the ring 22 and is thereby agitated and stirred up. It then passes along over the interior of the tube 24 and passes through the apertures 26 therein. Since the tube 24 is smaller in diameter than the screen 6, its surface speed is correspondingly less. This assists in the separating action. Fine material which passes through the apertures 26 into the space or compartment 3! travels downwardly toward the right of the figures and eventually discharged from the shell through appropriate peripheral openings 32. These are provided at suitable points so that the efiiux therefrom can discharge freely from the trommel into the saving and collecting structure, not shown.

In accordance with my invention, the normally imperforate blank section 2|, of no use in separating material, is made effective by the provision of an interior tube, such as 24. The inside tube, being of smaller diameter and being bounded by the rings 22 and 23, is effective to provide not only additional agitation of the material but likewise considerably augmented separation area.

What is claimed is:

1. A dredge trommel comprising a cylindrical shell adapted to be revolved about an inclined axis, said shell having a perforate portion and a generally imperforate portion, a supporting ring encompassing said generally imperforate portion, a perforate tube coaxially disposed within said shell and located adjacent to and coextensive with said generally imperforate portion only to leave an interior annular space between said tube and the generally imperiorate portion of said shell, annular imperforate rings extending between both ends of said tube and said cylindrical shell, there being openings through the generally imperforate portion of said shell into said space adjacent the lower end of said tube, and radial supports extending between said tube and the generally imperforate portion of said shell.

21%. dredge trommel comprising a support, a cylindrical shell mounted to rotate on said support about an inclined axis, said shell having a perforate portion including 'a circumferential series of apertures affording communication between the interior and the exterior of said shell, said shell having a generally imperfcrate portion including a circumferential imperforate area either side of said support and a series of circumferential openings on the other side of said support from said series of apertures, an interior tube within said shell and spaced therefrom to leave an annular compartment, said interior tube being axially coextentween the interior and the exterior of said shell,

sive with said generally imperforate portion 7 and overlying said openings, and spacers for holding said tube in position with respect to said shell having a generally imperforate portion including a circumferential imperforate area either side of said support and a series of circumferential openings on the other side of said support from said series of apertures, an interior tube within said shell and spaced therefrom to leave an annular compartment, said interior tube being axially coextensive with said generally imperforate portion and overlying "said openings, and imperforate rings at the upper and lower ends of said compartment for holding said tube in position with respect to said shell, said tube having perforations therein constituting a substantial continuation of said apertures, overlying said generally imperforate portion and overlying said openings for passing material from within said tube into said compartment for discharge from said compartment through said openings.

4. A dredge trommel comprising a support, a cylindrical shell mounted to rotate on said support about an inclined axis, said shell having a perforate portion including a circumferential series of apertures of predetermined size affording communication between the interior and the exterior of said shell, said shell having a generally imperforate portion including a circumferential imperforate area either side of said support and a series of circumferential openings of substantially larger size than said predetermined sized apertures disposed on the other side of said support from said series of apertures, an interior tube Within said shell and spaced therefrom to leave an annular compartment, said interior tube being axially coextensive with said generally imperforate portion and overlying said openings, and spacers for holding said tube in position with respect to said shell, said tube having perforations of substantially said predetermined size therein and constituting a substantial continuation of said apertures, overlying said generally imperforate portion and overlying said openings for passing material from within said tube into said compartment for discharge from said compartment to said openings.

EDWARD OLSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 419,465 Mitchell Jan. 14, 1890 632,637 Brooker Sept. 5, 1899 983,495 I-Iunnicutt Feb. 7, 1911 1,064,989 Palmer June 17, 1913 1,182,680 Hemings May 9, 1916 1,585,242 Hogeman May 18, 1926 1,770,977 Fowden July 22, 1930 1,865,094 Freden June 28, 1932 1,960,085 Goldberg May 22, 1934 

